I am new to using MD and Lammps. I am trying to simulate the fusion of a mixture of oxides.
I am putting the ions as charged particles. As a potential I would be interested in using a Born Mayer Huggins (BHM) (https://lammps.sandia.gov/doc/pair_born.html) and with coulomb interaction.
I read in the manual about the potential and it is not clear to me how the C coefficient of the coulombic part is included. The manual states that
"The styles with coul / long or coul / msm add a Coulombic term as described for the lj / cut pair styles."
but the arguments in the example are
pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
As far I understand, this coefficient are A (6.08) sigma (0.317), rho (2.340), C (24.18), D (11.51)
Could you explain me how to include the coefficient C of the Coulomb interaction?
Another question. in my system have to type of structural units AB3 or AB4 with defined angles. I am traing to include, also, an Angel Potential like this.
angle_style harmonic
angle_coeff 1 300.0 107.0
How can define for two type of strcutural units?
Thanks very much for your help
I am new to using MD and Lammps. I am trying to simulate the fusion of a
mixture of oxides.
I am putting the ions as charged particles. As a potential I would be
interested in using a Born Mayer Huggins (BHM)
(https://lammps.sandia.gov/doc/pair_born.html) and with coulomb interaction.
I read in the manual about the potential and it is not clear to me how
the C coefficient of the coulombic part is included. The manual states that
“The styles with coul / long or coul / msm add a Coulombic term as
described for the lj / cut pair styles.”
but the arguments in the example are
pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
As far I understand, this coefficient are A (6.08) sigma (0.317), rho
(2.340), C (24.18), D (11.51)
Could you explain me how to include the coefficient C of the Coulomb
interaction?
those are two different constants. the factor “C” in the coulomb expressions is 1/(4pieps_0*eps) times a conversion constant that depends on the choice of units. this conversion factor is set implicitly through the choice of units.
Another question. in my system have to type of structural units AB3 or
AB4 with defined angles. I am traing to include, also, an Angel
Potential like this.
angle_style harmonic
angle_coeff 1 300.0 107.0
How can define for two type of strcutural units?
i don’t understand what is the issue here?
these kind of angle interactions have to be defined explicitly and they have to be assigned an angle type and thus you can assign different parameters to different angle types.
axel.
Dear Axel,
Thanks for your response! I include some comments between lines